1. Field
One or more example embodiments of the inventive concepts relate to a backside illumination image sensor. One or more other example embodiments of the inventive concepts relate to an image processing system.
2. Description of the Related Art
A complementary metal oxide semiconductor (CMOS) image sensor (CIS) includes a plurality of pixels. The CIS converts an optical image signal detected by each of the pixels into an electrical image signal. The CIS includes a plurality of MOS transistors corresponding to a pixel, and detects and processes an output signal of the pixel using the MOS transistors. More specifically, each pixel includes a photodiode for detecting an incident optical image signal and a plurality of MOS transistors for converting the optical image signal into an electrical image signal.
The CIS is driven using the simpler method than a charge-coupled device (CCD) image sensor and can employ various scanning methods. In addition, circuits for processing signals output from pixels are integrated into a single chip using a CMOS process. Therefore, the CIS has the advantages of having a relatively small size, low manufacturing cost, and low power consumption when compared to a CCD image sensor.
One such single chip technique includes integrating an analog-to-digital converter (ADC) that converts an analog signal output from a pixel array into a digital signal and an image signal processor (ISP) that processes the digital signal output from the ADC into an image signal into a single chip.
In high-illumination environments, the average brightness of a frame defined by frame data output from an image sensor has a very big value. Contrarily, in a low-illumination environment, the average brightness of a frame output from the image sensor has a very small value.
Accordingly, it is difficult to process an electrical image signal, i.e., frame data output from the image sensor in the high- or low-illumination environments. In addition, pixels in the image sensor may have different sensitivity, and therefore, it may occur that only some of the pixels are saturated.